It has become relatively common for individuals to possess a number of different devices through which they communicate. For example, a person may have a home telephone, a wireless telephone, a pager and an office telephone. As the population becomes increasingly mobile, making contact with a person through one of these communication devices has become more difficult.
Call forwarding is one method of addressing this problem. Certain telephone systems allow users to enter another number to which a call is forwarded if not answered by a specified number of rings. This should allow an individual with multiple telephone devices to forward the call to such devices until the telephone at which the individual is located finally rings. However, if several telephones are involved, this approach becomes complicated. Moreover, it requires the calling party to remain on the line for a significant period of time if the call is to be forwarded multiple times. Furthermore, it is necessary that call forwarding capabilities exist on each of the individual's telephones. In addition, this approach requires that all telephones involved be reprogrammed each time an individual desires to initiate call forwarding. A significant drawback to this forwarding strategy is that, in each leg of the forwarded call, the calling party is terminated on the last device or network in the chain. It follows that the final number in the forwarding scheme is responsible for all available enhanced services or voice mail available to the caller. Accordingly, although a call may have been initially placed to an office telephone equipped with voice mail and/or operator assist, all such enhanced services of the corporate network are lost once the call is forwarded off the corporate PBX (e.g., to the user's wireless telephone).
Travel can also exacerbate the difficulty of establishing communication with an individual having access to multiple telephone devices. Upon checking into a hotel, the telephone in a traveler's hotel room becomes available as yet another potential means of contact. Unfortunately, this forces a calling party to decide whether to attempt to contact the traveler through his or her room telephone or other telephone device (e.g., wireless telephone or pager). If the traveler does not answer the called telephone, the calling party then must decide whether to leave a message (unaware of when, or if, the message will be retrieved) or instead attempt to reach the traveler via his or her other telephone. Likewise, if the traveler is expecting an important call but is unsure whether it will be placed to his room telephone or wireless telephone, the traveler may feel compelled to remain within his room until the call has been received. In addition, if the traveler's wireless telephone does not support certain types of long distance calls (e.g., to various foreign countries), the traveler may be able to place certain types of calls only from his or her hotel room.
The office telephone is the primary point of contact of most business people. Typically, corporations invest significantly in their office telephone infrastructure, which often includes voice mail, paging and unified messaging systems. In addition, most corporations have negotiated contracts with their telephone carriers (e.g., local and long distance carriers) to ensure they obtain the lowest possible rates for calls placed via their corporate network. However, because the corporate workforce is becoming increasingly mobile, more business people are using wireless telephones to conduct their business when they are out of the office. This has resulted in corporations spending a larger portion of their telecommunications budget on wireless communications, with far less favorable negotiated rates than the rates of their corporate network. In addition, wireless communication systems often lack the enhanced conveniences (e.g., interoffice voice mail, direct extension dialing, etc.) that corporate users have come to expect in the office environment.
A solution to the aforementioned problems would be to allow wireless telephony devices (e.g., wireless telephones or pagers) to access an office telephone system as though they were desktop telephones connected to the company's PBX. It is desirable to incorporate wireless devices into the PBX network so that users may place and receive telephone calls using the office PBX telephone system even though they are at a remote location (e.g., out of the office). This would allow the enhanced conveniences of today's PBX networks (e.g., interoffice voice mail, direct extension dialing, etc.) to be available on wireless devices—something which is desperately needed in today's society.
There have been recent attempts to incorporate wireless telephones into PBX networks. One system provided by Ericsson, requires the creation of a mini-cellular network within the confines of the enterprise. A cellular switching unit, unique wireless telephones and an auxiliary server are required to route inbound telephone calls to a wireless handset serving as a remote office telephone.
An in-building wireless system has been proposed by Nortel Networks. This system requires the wiring of pico-cells throughout the enterprise's building. The system routes inbound telephone calls to specialized wireless telephones serving as additional office PBX telephones. The wireless telephones cannot be used as conventional standard wireless telephones until they leave the premises.
These systems allow inbound calls to be routed to an office telephone and a wireless telephone, but they are not without their shortcomings. For example, each system requires specialized cellular equipment and wireless handsets. Moreover, the systems only use the wireless telephones for inbound telephone calls. In addition, these systems cannot use the wireless telephone as a conventional wireless telephone (i.e., not part of the enterprise's PBX network) within the building.